Skid steer loaders were first invented about 30 years ago to fill a need for a small, highly maneuverable vehicle that was capable of carrying an implement mounted on loader arms. Skid steer loaders are typically small vehicles, on the order of 10 to 14 feet long that rest on four or more wheels, at least two of which being disposed on each side of the vehicle.
In order to turn these vehicles, the wheels on opposing sides of the skid steer loader are driven at different speeds. This causes the faster moving wheels on one side to advance that side over the ground faster than the other side on slower moving wheels. The effect is to turn the vehicle toward the wheels on the slower moving side. Since the wheels are not turnable with respect to the vehicle, the vehicle turns by skidding slightly, hence the name “skid steer loader.”
In the extreme case the wheels on one side of the vehicle not only rotate slower than the wheels on the other side of the vehicle but can turn in the opposite direction. When this mode of operation is selected, the skid steer loader will rotate in place about a vertical and generally stationary rotational axis. This mode of operation requires the greatest amount of wheel skidding and as a consequence creates ruts and wears tires.
This ability to change direction by rotating about an axis within the footprint or perimeter of the loader itself was the primary reason why the skid steer loader achieved its great success.
Steering by skidding does place an extreme strain on the suspension components of the vehicle. For this reason traditional skid steer vehicles have no sprung suspensions. Instead, they have axles mounted directly to the sidewalls of the skid steer vehicle. Their axles are usually fixed with respect to the vehicle's sidewalls and the wheels are bolted on the ends.
In the traditional skid steer vehicle, the wheels on each side of the vehicle are driven by a link belt (e.g. a chain). The belts are contained in one or two chain tanks that are located inside the body of the vehicle. These tanks are typically formed from structural members of the vehicle such as the steel sidewalls of the chassis. These structural members are sealed to create fluid tight tanks that are filled with lubricant. When the belts are driven by hydraulic motors, they run through the lubricant in the tanks.
New skid steer vehicles having sprung suspensions have been devised in recent years, several of them by the inventors of this patent application. These suspensions typically employ gears and shafts.
This use of a gear and shaft arrangement requires significant additional manufacturing cost, due to the need to make custom gears, accurately machine shafts, and accurately locate the shafts with respect to one another.
The use of gears and shafts also increases the unsprung weight of the vehicle and the overall dimensions of the housings in which the gears are mounted.
What is needed, therefore, is a skid steer vehicle having a reduced unsprung weight. What is also needed is a skid steer vehicle having belts coupling the vehicle's drive motors with the driven wheels. What is also needed are vehicle belt drive housings that are configured to internally support drive belts. What is also needed is a belt drive arrangement that accommodates a sprung suspension.